The Washington Post offers some first-day flavor. The new operating system isn't dominating Google search or Twitter traffic, a usually insightful barometer of how people are reacting to news. More directly, there are links in the story to writer Rob Pegoraro's own review and reaction from Walt Mossberg at The Wall Street Journal, David Pogue at The New York Times and PCMag.com's Sascha Segan, who looks at the first three WP7 phones released in the States: The HTC Surround, the and Samsung Focus (AT&T) and the HTC HD7 from T-Mobile.

The quality of the operating system will only be part of the equation determining WP7's success or failure. The positives for the OS include the close tie to Microsoft's stable of productivity products and other platforms, including Lync, which is slated to debut Nov. 17. It remains to be seen whether Microsoft's enormous influence is enough to enable it to carve out a niche among the exploding wireless segment, which is now led by Android.

There clearly is a lot on the line for Microsoft. Paul McDougall at InformationWeek does a good job of lining up the dynamics for the software giant, and it pretty much reads like a status report on the Dallas Cowboys or the Democratic Party. Just about everything the company is trying isn't working; its desktop OS dominance is akin to dominating the horse whip business a few years after the automobile was invented. McDougall, who thinks CEO Steve Ballmer's job is in jeopardy, writes that the quality of WP7 might not matter:

most analysts believe the offering, though slick in many respects, is too little, too late to meaningfully bolster the company's meager 5% share of the mobile OS market.

Even Ray Ozzie, Microsoft's departing chief software architect, thinks the day of the PC is passing. The big question, then, is whether the company will find something, or some things, to replace it. A major step toward answering that question was just introduced to the U.S. market.